Outdoor luminaires which are utilized for wide area lighting or street lighting face many challenges during the life of the luminaire. Due to the environmental circumstances and conditions in which the luminaires are utilized, and due to the extensive heating and cooling cycles inflicted upon the electrical and optical system of the luminaire, dirt, dust and moisture intrusion commonly occur into the electrical and optical system thereby affecting the lighting characteristics of the luminaire over time. The penetration of these foreign substances into the luminaire therefore must be taken into account during the design phase of the reflector and light system in order to maintain continued output characteristics over a given length of time. Penetration ratings are provided in order to describe the ability for luminaire housings as well as various optical systems to resist the penetration of both solids and liquids into the sealed compartment defining the optical area. These intrusion protection or ingress protection ratings are designed to help gauge the ability for the seals to inhibit dirt and other foreign material from entering into the luminaire and causing potential performance loss. Commonly, outdoor luminaires have interpenetration protection ratings (IP) in order to gauge the performance of the seals and their ability to prevent dirt and foreign substance intrusion. Intrusion by both foreign substances such as dirt and water on the lenses and other reflective elements of the luminaire affects the performance of the lighting system. The luminaire dirt depreciation for particular conditions in which the luminaire will be installed thus comes in handy to determine overall light loss and maintenance required in order to maintain the luminance or illumination level of the luminaire. By preventing the intrusion of moisture or other foreign substances into the optical system, lower initial lumen output and therefore lower wattage lamps, may be utilized.
It is thus desirable to provide an outdoor luminaire which has adequate seals which prevent contaminates such as dust, soot or moisture to collect on the optical system surfaces. This is particularly the case given that these sealed compartments or optical systems undergo intense heating and cooling cycles, thereby changing the pressure differential between the sealed interior space defined within the globe or other optical system area and exterior of the globe, as can be commonly understood. When activated, the lamp causes intense heat within the optical area thereby increasing the air pressure therein and creating a positive pressure system between the sealed internal area or compartment of the luminaire and the exterior area. During cooling, a reverse air pressure system ensues thereby exerting opposite pressure on the seals of the sealed compartment while the system cools thereby allowing inflow of contaminates and other material into the sealed compartment. It is thus desirable to provide a sealed outdoor luminaire which has adequate seals which allow outflow of air from inside the globe or optical area during intense heating and which restricts the inflow of contaminates and other material into the luminaire compartment during the cooling cycle or other negative pressure event.
Interpenetration protection ratings for luminaires are often quoted as indicated above for lighting enclosures and luminaires and indicate protection from solids, liquids and impact. Various standards are known for describing the ratings and typically, the IP rating is given with two numbers, the first number indicating the protection against solids while the second number indicating the protection against liquids. It is desirable to provide an IP rating of a luminaire over its lifetime of a minimum of IP66 indicting that there is total protection against dust intrusion and also high protection against liquids. Various other IP ratings may be implemented as it is significantly desirable to provide intrusion protection of dust and other contaminates in the interior portion of the optical area, the optical system of a luminaire including the lamp or other light generating mechanism or component, baffles, shields, reflectors and other elements located within the globe and including the globe.